UPDATE 7.51pm: JULIA Gillard has dismissed as "stupid and wrong" a senior union official's belief that the 9/11 attacks were a conspiracy but has refused to discipline him.

Kevin Bracken, the president of the Victorian Trades Hall and secretary of the Maritime Union of Australia, sparked anger this morning after claiming the attacks were not the result of terrorist activity.

"I believe the official story is a conspiracy theory that doesn't stand up to scientific scrutiny," Mr Bracken told ABC talk-back host Jon Faine.